Once a product is designed and manufactured, it may under go modifications that are implemented in subsequent units that are manufactured. Changes are made to make the product safer, lower cost, add functions, etc. to meet changes in the market. These changes are called Engineering Changes because the change usually requires a change in the design specification by engineering. A change to the product usually changes the manufacturing process that produces the product. To assure that changes to designed functions of the product are reflected in the manufactured product, most organizations use an engineering change control process that requires that the manufacturing process changes are in effect before the changed product is manufactured. Each manufactured product may be tracked by a designation of the engineering change to which the product was manufactured. The item identifier, called a part number may be changed or a secondary identifier called a revision or engineering change level may be changed to signify that the product has been changed from the previous design of the product. Many processes and systems have been developed to assure that the manufacturing process changes are made to reflect the engineering change before the product is manufactured.
Many of these changes are unanticipated and there may be units of the product in the manufacturing process when an engineering change is contemplated or implemented. The product units may be allowed to complete the manufacturing process and shipped at the original design. However, it may be economically feasible to modify (rework) units in the manufacturing process so that these units meet the changed requirements. The prior art describes for some products, especially semiconductor products, where the product design, with in limits, can accommodate engineering changes without major reprocessing of the product.
However, the implementation of the engineering change to product units in the manufacturing process have been controlled and tracked manually. With a manual process, there are “escapes” where product units that should have been reworked are not, product units that were thought to have been reworked are not, and product units that should not be reworked are reworked. With a manual process, the wrong rework processes may used to rework product units. The rework process may be dependent on the state of unit in the manufacturing process. A unit that has just started may require just a change in a component in the bin used to assemble the product. A unit later in the process may require a component to be removed and another assembled in its place. A unit near completion, for example after encapsulation, may not be reworked. A unit may continue in the original manufacturing process to a specified point, then reworked to the engineering change specification. After a unit is reworked, the unit may require a different manufacturing process than before rework. For example, a test to validate the rework is executed.
The part identifier of a unit is associated with the engineering specification to which it was manufactured. The part identifier is usually called a part number and may also include a secondary identifier called Engineering Change level (E/C level) or revision level. When a unit built to a first engineering specification is reworked to a second engineering specification, the part identifier for the unit is changed to that associated with the second engineering specification.
The MES uses work order to associate a part identifier and quantity with units to be manufactured. The MES also associates a route, a step-by-step sequence of manufacturing process steps, to a work order as the operational description of the manufacturing process. The MES uses the route to control and track the units in the manufacturing process.
When an engineering change is contemplated and designed, product units may continue to be manufactured. These units may not be useable or may require more rework than if stopped when the engineering change was contemplated. Stopping the manufacturing process will provide the opportunity to assess the quantity of product in the manufacturing process and the state of the units in the process. An economic decision can be made as to if and when the engineering change can be implemented. It may be desirable to permit units to proceed to a specified point in the manufacturing process before stopping.
The product is controlled and tracked in the manufacturing process using a manufacturing execution system, MES, or shopfloor system. The present invention is a function of an MES to assure accurate implementation of an engineering change by:                1) Identifying the product units for implementation of the engineering change        2) Stopping the product in the manufacturing process while allowing other products to continue manufacturing. The stopping point in the manufacturing process can be specified        3) Proving a view of the units in the process so that an assessment of the impact engineering change can be made. The state of each unit or group of units can be determined so that rework instruction can be developed dependent on the state of the unit to be reworked.        4) Providing the rework instructions or process to implement the engineering change to each unit. The rework instructions may be a function of the state of manufacturing process of the unit. The rework can be applied at a specified point in the manufacturing process.        5) Tracking when a unit is reworked. Assure that all units to be reworked are reworked        6) Providing the manufacturing process for the unit after rework.        7) With each unit reworked, in the associated work orders, decrementing the number of units with the original product identifier and incrementing the number of units with the engineering change product identifier.        